Method of making acetyl salicylic acid



Patented Oct. 26, 1926.

I UNITED STATES PATENT OFFICE.

DONAIJD ARCHER NIGHTINGALE, OF AMBLER, PENNSYLVANIA, ASSIGNOR TO THE KE'IOID COMPANY, OF WILMINGTON, DELAWARE, A CORPORATION OF DELAWARE.

METHOD OF MAEING ACETYL SALIOYLIG ACID.

No Drawing. Application filed July 22, 1924, Serial No. 727,488. Renewed larch 1d, 1926.

My invention relates to the manufacture of dthe mono acetic acid ester of salicylic aci This substance, more usually known as 5 acetyl salicylic acid (and to trade as aspirin) is commonly prepared from salicylic acid, acetic acid and acetic anhydride. The process is somewhat tedious in that it involves fractional crystallization, with its at- 1 tendant losses.

The object of my invention is to provide a cheaper and more rapid methodof me tiufac turing acetyl-salicylic acid of a high degree of purity, with a practically quantitative yield. I

My invention is based on my discover that keten when brought in contact wit salicylic acid will effect a rapid esterification of the salicylic acid by direct addition and therefore without the formation of water of decomposition, which is a drawback to the old method, and my invention consists broadly speaking in the method of manufacturing acetyl salicylic acid by bringing keten into contact with salicylic acid.

The time required for this reaction is considerably shortened by the use of a mutual solvent. For example: A given quantity of salicylic acid is dissolved in about five times its weight of dry ethyl ether. Keten (C H O) is'passed through the solution to the point of saturation. On evaporation of the ether there remains a mass of needle-- like crystals of acetyl salicylic acid.

The reaction that takes place may be mp resented by the following equation:

Having now described my invention, what I claim as new and desire to secure by Let- 40 ters Patent,- is:

1. The method of manufacturing acetyl salicylic acid which comprises reacting upon salicylic acid with keten.

2. The method of manufacturing acetyl salicylic acid which comprises-reacting upon salicylic acid with keten in the presenceof a neutral solvent which is also a solvent of keten. 1

3. The method of manufacturing acetyl salicylic acid which consists in dissolving salicylic acid in a neutral solvent which is also a solvent ofketen and passing keten gas through the solution.

DONALD A. NIGHTINGALE. 

